This study investigated the effects of low doses of caffeine on 100-m swimming performance. Elite swimmers (N = 15) undertook a 100 m "race” on two occasions one week apart, 60 minutes after consuming either 2 mg/kg caffeine or a placebo. Diet and training were standardized for 24 hours before the trials and the warm-up prior to each race. Swimmers performed their preferred stroke. Ss completed a questionnaire that tracked their sleep patterns for the evening after each "race”.

There was no performance enhancement in reaction time, 50-m split time, or 100 m time for the caffeine trial compared with placebo. However, ratings of perceived effort were lower for the caffeine trial. Self-reported measures of sleep were affected by caffeine supplementation increasing the time taken to fall to sleep and reducing the self-rating of quality of sleep.

Implication. Sprint swimming performance was not improved following supplementation with low levels of caffeine. Caffeine intake did affect post-race sleep and is an important consideration in sports in which an athlete must compete over several days.